But it was not clear how the firm could stop Belarus carrying out its threat to cut power supplies to pipeline pump stations, so halting the flow of gas onward to Europe.
Gazprom managers and Belarus negotiators led by Vladimir Semashko, the first deputy prime minister were locked in last-ditch talks as most Russians prepared to greet the New Year.
"The talks are continuing, but unfortunately they have led to no results so far," Gazprom spokesman Sergei Kupriyanov said as the negotiations entered their sixth hour. "We want to reach an agreement and prevent events turning into a crisis."
"If the deal is not signed ... We will be forced (on January 1) to suspend supplies for Belarus' domestic needs. As for the transit shipment contracts beyond Belarus, they will be met in full."
But earlier, Alexander Ozerets, Belarus’s energy minister, said if Gazprom cut deliveries for Belarus's domestic use, his country would disable the Yamal-Europe pipeline, which carries all Russian gas transiting Belarus to Western Europe.
"In the event that gas supplies to Belarus are cut off we will in turn cut off the power supply to gas compressor stations on the Yamal-Europe pipeline," Ozerets told Reuters.
He said though he believed there was a real prospect of a deal being signed before the deadline.
Gazprom export chief Alexander Medvedev warned Belarus against disrupting export supplies.
"The Yamal-Europe pipeline belongs entirely to Gazprom. Disrupting transit shipments is unacceptable," he told Reuters via his spokesperson.
Medvedev declined to comment though on how Gazprom could prevent Belarus from disabling the pipeline.
The contract under which Gazprom has been supplying gas to Belarus - at a massively discounted price of $46 per 1,000 cubic metres - expires at midnight on Sunday. By comparison, Gazprom charges European customers over $250.
Gazprom wants Belarus to pay $105 from 2007, a demand it says is part of the firm's campaign to bring the amounts Russia's ex-Soviet neighbours pay for their gas into line with world prices.